ANNULOSA JAVANICA. 33 
froy. Still, however, the Dytisci and Hydrophili were kept close to each other as neighbouring 
groupes by Linnzeus, Geoffroy, Fabricius, and Olivier, until M. Latreille thought proper to 
separate them. 
Olivier seems to have well remarked that Degeer’s opinion as to the number of joints in the an- 
tenne of Hydrophilus piceus being only nine, is founded rather on appearance than on truth, and 
that the real number corresponds with that of the Dydisci, namely eleven, the only difference 
being that the eighth and tenth joints are here very minute. Their place is marked by the dis- 
tances which intervene between what are commonly considered the second and third, and the 
third and last joints of the clava. The fact however is, that the number of joints in the antenne 
is in these two stirpes subject to some variation from the typical number, which in Coleoptera 
is eleven. 
I have already alluded to those two divisions of the maxilla in /7ydrophilus of which one cor- 
responds with what is usually termed the internal maxillary palpus in ddephaga, although it now 
ceases to be palpiform. In some genera however, such as Sperchews, which come nearest to 
the Hydradephuga, the outer process of the maxilla is long, slender, and truly palpiform. Fabri- 
cius accordingly, when he instituted the genus Spercheus assigned six palpi to it, as well as to 
Dyliscus. The feet, indeed, of the Philhydrida, as well as other points of their external anatomy, 
their larva: and their habits, all prove their affinity to the Mydradephaga. 
The larva of Hydrophilus piceus is long and somewhat conical, and bears great resemblance to 
that of a Dytiscus, the body being terminated in both by twe filiform processes, which seem useful 
for the respiration of the insect. One grand difference between them, as Lyonnet has shown in 
contravention of a curious fancy of M. Frisch, is that the head of the larva of Hydrophilus being 
adapted to its habit of preying on small mollisca as they float in the water, is inclined towards 
its back, whereas in the other it has its usual inclination towards the belly. Both larvee are thus 
carnivorous, quit the water when full-grown, and having made an oyal cocoon, undergo meta- 
morphosis in the earth. 
The Philhydrida appear, when arrived at their perfect state, to be insome degree herbivorous, 
or at least to lose in a great measure the carnivorous habits of the Hydradephaga ; they seem 
therefore to indicate an approach towards insects truly herbivorous. Perhaps Zydrophilus piceus 
is as voracious an animal as belongs to the stirps; yet we may learn how inferior it is in voracity 
to an Adephagous insect, from the anecdote recorded by Clairville, on the authority of Dr. Es- 
per, who having confined an insect of this species in a glass of water with a Dydiscus marginalis, 
not more than half its size, soon found it yield itself an easy prey to the latter, which having 
detected a vulnerable part between the head and thorax, greedily devoured it. M. Miger, also, 
who observed so well the singular manners of this family, and who has given so detailed an ac- 
count of them in the fourteenth volume of the Anales du Muséum, ascertained that the greatest 
part of the food of the perfect insects is derived from aquatic plants. 
I shall offer the following arrangement of the Philhydrida as an approximation to the natural 
one: 
F Philhydrida 
